1. Field of the Invention
This invention relates to a digital electronic still camera of the type wherein a still picture image picked up by a solid state image pickup element is recorded into a record medium.
2. Description of the Prior Art
A digital electronic still camera of the type wherein a pickup image signal outputted from a solid state image pickup element is converted into a digital signal and then recorded into a semiconductor memory or a magnetic disk or the like is conventionally known. An exemplary one of such conventional digital electric still cameras is disclosed, for example, in U.S. Pat. No. 4,131,919.
Referring to FIG. 6, there is shown an exemplary one of such conventional digital electronic still cameras. The digital electric still camera shown includes a lens 101, an aperture diaphragm 102, a half mirror 103 for introducing a picture image to a viewfinder (not shown) of the camera, an optical low-pass filter 104, a CCD (charge coupled device) image sensor 105, and a driver circuit 106 for driving the CCD image sensor 105. The digital electric still camera further includes a processing circuit 107 for performing video signal processing of a pickup image output signal produced from the CCD image sensor 105, a sample-and-hold circuit 108 for sampling and holding therein a pickup image output signal after video signal processing by the processing circuit 107, and an AD (analog to digital) converter 109 for converting a pickup image output signal obtained by sampling and holding by the sample-and-hold circuit 108 into a digital signal. The sample-and-hold circuit 108 and the AD converter 109 may be a general purpose unitary device on the market. The digital electronic still camera further includes a latch circuit 110 for latching therein picture image information in the form of digital signal received from the AD converter 109, and a digital memory 111 for storing therein picture image information latched in the latch circuit 110. The digital electronic still camera further includes a magnetic disk apparatus 112 for storing still picture information from the digital memory 111 onto a magnetic disk, a release switch 113 for starting a picking up operation of a still picture image by the CCD image sensor 105, and a timing controlling circuit 114 for controlling operation of the circuits 106 and 108 to 111 and the magnetic disk apparatus 112.
Such conventional digital electronic still camera is provided principally in order that a picture image picked up thereby may be displayed on a television receiver for domestic use, and the CCD image sensor 105 for use with such conventional digital electronic still camera involves 400 thousand picture elements or so to the utmost. Accordingly, a photograph taken with such conventional digital electronic still camera cannot bear comparison with a photograph taken otherwise with a conventional silver salt camera. Meanwhile, a magnetic record disk is only required to have a recording density corresponding to the density of picture elements of the CCD image sensor 105 or so, and besides, from the necessity to make a disk compact, the recording capacity of such disk is very limited.
Meanwhile, development of image pickup elements or improvement in recording density of record media in recent years is remarkable. Thus, elements having a performance which could not have been imagined at an initial stage of development of such conventional digital electronic still cameras have been developed.
However, since such conventional digital electronic still camera has a specification conforming to a television receiver for domestic use, even if a CCD image sensor for a high quality television camera of further high integration is developed, such CCD image sensor cannot be utilized for the conventional digital electronic still camera. Further, as a record medium, a writable optical disk has been developed in recent years, and the recording density has been raised remarkably with such writable optical disk. However, since the amount of information of a signal picked up by a CCD image sensor of a conventional digital electronic still camera is small, an optical disk is too great in recording capacity to use the same for such application.
Such problems arise from the fact that the specification is commonplace regardless of development of elements, and if the specification follows up such development of elements, then there is no problem. However, it is not possible to establish a plurality of specifications forecasting possible development of elements in advance, and it does not provide any merit to a user who has bought a product of a preceding specification to re-examine and revise a specification so as to assure the high order compatibility each time an element is developed.